Planetary gear train of automatic transmission for vehicle

ABSTRACT

A planetary gear train of an automatic transmission for a vehicle may include an input shaft configured for receiving an engine torque, an output shaft configured for outputting a shifted torque, a first planetary gear set including first, second, and third rotation elements, a second planetary gear set including fourth, fifth, and sixth rotation elements, a third planetary gear set including seventh, eighth, and ninth rotation elements, a fourth planetary gear set including tenth, eleventh, and twelfth rotation element, and six control elements for selectively interconnecting the rotation elements and a transmission housing.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority to Korean Patent Application No.10-2015-0147620, filed Oct. 22, 2015, the entire contents of which isincorporated herein for all purposes by this reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to an automatic transmission for avehicle.

Description of Related Art

Recent increases in oil prices are triggering hard competition amongauto-makers in enhancing fuel consumption of a vehicle.

In this sense, research is being conducted on engines in terms ofreducing weight and improving fuel efficiency by down-sizing, andresearch is also being conducted to ensure both drivability andcompetitiveness for maximizing fuel efficiency by implementing anautomatic transmission with multiple speed stages.

However, in the case of the automatic transmission, the number ofinternal components increases as the number of gear shift stages isincreased, which may deteriorate installability, production cost, weightand/or power flow efficiency.

Therefore, in order to maximally enhance fuel consumption of anautomatic transmission having increased shift stages, it is importantfor improved efficiency to be derived by a smaller number of parts.

In this respect, an eight-speed automatic transmission has been recentlyintroduced, and a planetary gear train for an automatic transmissionenabling more shift stages is under investigation.

Considering that gear ratio spans of recently developed eight-speedautomatic transmissions are typically between 6.5 and 7.5, fuelconsumption enhancement is not very large.

In the case of a gear ratio span of an eight-speed automatictransmission having a level above 9.0, it is difficult to maintain stepratios between adjacent shift stages to be linear, by which drivingefficiency of an engine and drivability of a vehicle deteriorated.

Thus, research studies are underway for developing a high efficiencyautomatic transmission having nine or more speeds.

The above information disclosed in this Background section is only forenhancement of understanding of the background of the invention andtherefore it may contain information that does not form the prior artthat is already known in this country to a person of ordinary skill inthe art.

BRIEF SUMMARY

Various aspects of the present invention are directed to providing aplanetary gear train of an automatic transmission for a vehicle havingadvantages of, by minimal complexity, realizing at least nine forwardspeeds and at least one reverse speed, increasing a gear ratio span soas to improve power delivery performance and fuel consumption, andachieving linearity of shift stage step ratios.

According to various aspects of the present invention, a planetary geartrain of an automatic transmission for a vehicle may include an inputshaft for receiving an engine torque, an output shaft for outputting ashifted torque, a first planetary gear set including first, second, andthird rotation elements, a second planetary gear set including fourth,fifth, and sixth rotation elements, a third planetary gear set includingseventh, eighth, and ninth rotation elements, a fourth planetary gearset including tenth, eleventh, and twelfth rotation elements, and sixcontrol elements for selectively interconnecting the rotation elementsand a transmission housing, in which the input shaft may be continuouslyconnected to the third rotation element and selectively connected toeighth rotation element, the output shaft may be continuously connectedto the second rotation element and the eleventh rotation element, thefourth rotation element may be continuously connected to thetransmission housing, the fifth rotation element may be continuouslyconnected to the ninth rotation element, the sixth rotation element maybe continuously connected to the tenth rotation element, and at leastnine forward speeds and at least one reverse speed are achieved bycontrolling three of the six control elements.

The third rotation element may be selectively connected to the seventhrotation element by a first clutch, the eighth rotation element may beselectively connected to the input shaft by a second clutch, the sixthrotation element may be selectively connected to the eighth rotationelement by a third clutch, the first rotation element may be selectivelyconnected to the twelfth rotation element by a fourth clutch, the eighthrotation element may be selectively connected to the transmissionhousing by a first brake, and the twelfth rotation element may beselectively connected to the transmission housing by a second brake.

The first, second, and third rotation elements may be respectively a sungear, a planet carrier, and a ring gear of the first planetary gear set,the fourth, fifth, and sixth rotation elements may be respectively a sungear, a planet carrier, and a ring gear of the second planetary gearset, the seventh, eighth, and ninth rotation elements may berespectively a sun gear, a planet carrier, and a ring gear of the thirdplanetary gear set, and the tenth, eleventh, and twelfth rotationelements may be respectively a sun gear, a planet carrier, and a ringgear of the fourth planetary gear set.

According to various aspects of the present invention, a planetary geartrain of an automatic transmission for a vehicle may include an inputshaft for receiving an engine torque, an output shaft for outputting ashifted torque, a first planetary gear set including first, second, andthird rotation elements, a second planetary gear set including fourth,fifth, and sixth rotation elements, a third planetary gear set includingseventh, eighth, and ninth rotation elements, a fourth planetary gearset including tenth, eleventh, and twelfth rotation elements, sixcontrol elements for selectively interconnecting the rotation elementsand a transmission housing, a first connecting member connected to thefirst rotation element, a second connecting member connected to thesecond rotation element and the eleventh rotation element and directlyconnected to the output shaft, a third connecting member connected tothe third rotation element and directly connected to the input shaft, afourth connecting member connected to the fourth rotation element anddirectly connected to the transmission housing, a fifth connectingmember connected to the fifth rotation element and the ninth rotationelement, a sixth connecting member connected to the sixth rotationelement and the tenth rotation element, a seventh connecting memberconnected to the seventh rotation element and selectively connected tothe third connecting member, an eighth connecting member connected tothe eighth rotation element, selectively connected to the input shaftand the sixth connecting member, and selectively connected to thetransmission housing, and a ninth connecting member connected to thetwelfth rotation element, selectively connected to the first connectingmember, and selectively connected to transmission housing.

The first planetary gear set may be a single pinion planetary gear set,where the first rotation element may be a first sun gear, the secondrotation element may be a first planet carrier, and the third rotationelement may be a first ring gear, the second planetary gear set may be asingle pinion planetary gear set, where the fourth rotation element maybe a second sun gear, the fifth rotation element may be a second planetcarrier, and the sixth rotation element may be a second ring gear, thethird planetary gear set may be a single pinion planetary gear set,where the seventh rotation element may be a third sun gear, the eighthrotation element may be a third planet carrier, and the ninth rotationelement may be a third ring gear, and the fourth planetary gear set maybe a single pinion planetary gear set, where the tenth rotation elementmay be a fourth sun gear, the eleventh rotation element may be a fourthplanet carrier, and the twelfth rotation element may be a fourth ringgear.

The six control elements may include a first clutch selectivelyconnecting the third connecting member and the seventh connectingmember, a second clutch selectively connecting the input shaft and theeighth connecting member, a third clutch selectively connecting thesixth connecting member and the eighth connecting member, a fourthclutch selectively connecting the first connecting member and the ninthconnecting member, a first brake selectively connecting the eighthconnecting member and the transmission housing, and a second brakeselectively connecting the ninth connecting member and the transmissionhousing.

Shift stages realized by selective operation of the six control elementsmay include a forward first speed formed by simultaneous operation ofthe first and third clutches and the second brake, a forward secondspeed formed by simultaneous operation of the second and third clutchesand the second brake, a forward third speed formed by simultaneousoperation of the first and second clutches and the second brake, aforward fourth speed formed by simultaneous operation of the first andfourth clutches and the second brake, a forward fifth speed formed bysimultaneous operation of the first, second, and fourth clutches, aforward sixth speed formed by simultaneous operation of the second,third, and fourth clutches, a forward seventh speed formed bysimultaneous operation of the first, third, and fourth clutches, aforward eighth speed formed by simultaneous operation of the third andfourth clutches and the first brake, a forward ninth speed formed bysimultaneous operation of the first and fourth clutches and the firstbrake, and a reverse speed formed by simultaneous operation of the firstclutch and the first and second brakes.

According to various aspects of the present invention, a planetary geartrain of an automatic transmission for a vehicle may include an inputshaft for receiving an engine torque, an output shaft for outputting ashifted torque, a first planetary gear set as a single pinion planetarygear set including first, second, and third rotation elements, a secondplanetary gear set as a single pinion planetary gear set includingfourth, fifth, and sixth rotation elements, a third planetary gear setas a single pinion planetary gear set including seventh, eighth, andninth rotation elements, a fourth planetary gear set as a single pinionplanetary gear set including tenth, eleventh, and twelfth rotationelements, a first connecting member connected to the first rotationelement, a second connecting member connected to the second rotationelement and the eleventh rotation element and directly connected to theoutput shaft, a third connecting member connected to the third rotationelement and directly connected to the input shaft, a fourth connectingmember connected to the fourth rotation element and directly connectedto the transmission housing, a fifth connecting member connected to thefifth rotation element and the ninth rotation element, a sixthconnecting member connected to the sixth rotation element and the tenthrotation element, a seventh connecting member connected to the seventhrotation element and selectively connected to the third connectingmember, an eighth connecting member connected to the eighth rotationelement, selectively connected to the input shaft and the sixthconnecting member, and selectively connected to the transmissionhousing, and a ninth connecting member connected to the twelfth rotationelement, selectively connected to the first connecting member, andselectively connected to transmission housing, a first clutchselectively connecting the third connecting member and the seventhconnecting member, a second clutch selectively connecting the inputshaft and the eighth connecting member, a third clutch selectivelyconnecting the sixth connecting member and the eighth connecting member,a fourth clutch selectively connecting the first connecting member andthe ninth connecting member, a first brake selectively connecting theeighth connecting member and the transmission housing, and a secondbrake selectively connecting the ninth connecting member and thetransmission housing.

The first planetary gear set may include a first sun gear as the firstrotation element, a first planet carrier as the second rotation element,and a first ring gear as the third rotation element, the secondplanetary gear set may include a second sun gear as the fourth rotationelement, a second planet carrier as the fifth rotation element, and asecond ring gear as the sixth rotation element, the third planetary gearset may include a third sun gear as the seventh rotation element, athird planet carrier as the eighth rotation element, and a third ringgear as the ninth rotation element, and the fourth planetary gear setmay include a fourth sun gear as the tenth rotation element, a fourthplanet carrier as the eleventh rotation element, and a fourth ring gearas the twelfth rotation element.

According to various aspects of the present invention, a planetary geartrain of an automatic transmission for a vehicle may include an inputshaft for receiving an engine torque, an output shaft for outputting ashifted torque, a first planetary gear set as a single pinion planetarygear set including a first sun gear, a first planet carrier, and a firstring gear, a second planetary gear set as a single pinion planetary gearset including a second sun gear, a second planet carrier, and a secondring gear, a third planetary gear set as a single pinion planetary gearset including a third sun gear, a third planet carrier, and a third ringgear, a fourth planetary gear set as a single pinion planetary gear setincluding a fourth sun gear, a fourth planet carrier, and a fourth ringgear, a first connecting member connected to the first sun gear, asecond connecting member connected to the first planet carrier and thefourth planet carrier and directly connected to the output shaft, athird connecting member connected to the first ring gear and directlyconnected to the input shaft, a fourth connecting member connected tothe second sun gear and directly connected to the transmission housing,a fifth connecting member connected to the second planet carrier and thethird ring gear, a sixth connecting member connected to the second ringgear and the fourth sun gear, a seventh connecting member connected tothe third sun gear and selectively connected to the third connectingmember, an eighth connecting member connected to the third planetcarrier, selectively connected to the input shaft and the sixthconnecting member, and selectively connected to transmission housing,and a ninth connecting member connected to the fourth ring gear,selectively connected to the first connecting member, and selectivelyconnected to the transmission housing, and six control elementsselectively connecting the connecting members and the transmissionhousing.

A planetary gear train according to various embodiments of the presentinvention realizes at least nine forward speeds and at least one reversespeed formed by operating the four planetary gear sets as simpleplanetary gear sets by controlling six control elements.

In addition, a planetary gear train according to various embodiments ofthe present invention realizes a gear ratio span of more than 8.0,thereby maximizing efficiency of driving an engine.

In addition, the linearity of step ratios of shift stages is securedwhile multi-staging the shift stage with high efficiency, thereby makingit possible to improve drivability such as acceleration before and aftera shift, an engine speed rhythmic sense, and the like.

It is understood that the term “vehicle” or “vehicular” or other similarterms as used herein is inclusive of motor vehicles in general such aspassenger automobiles including sports utility vehicles (SUV), buses,trucks, various commercial vehicles, watercraft including a variety ofboats and ships, aircraft, and the like, and includes hybrid vehicles,electric vehicles, plug-in hybrid electric vehicles, hydrogen-poweredvehicles and other alternative fuel vehicles (e.g., fuel derived fromresources other than petroleum). As referred to herein, a hybrid vehicleis a vehicle that has two or more sources of power, for example, bothgasoline-powered and electric-powered vehicles.

The methods and apparatuses of the present invention have other featuresand advantages which will be apparent from or are set forth in moredetail in the accompanying drawings, which are incorporated herein, andthe following Detailed Description, which together serve to explaincertain principles of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an exemplary planetary gear trainaccording to the present invention.

FIG. 2 is an operational chart for respective control elements atrespective shift stages in the exemplary planetary gear train accordingto the present invention.

It should be understood that the appended drawings are not necessarilyto scale, presenting a somewhat simplified representation of variousfeatures illustrative of the basic principles of the invention. Thespecific design features of the present invention as disclosed herein,including, for example, specific dimensions, orientations, locations,and shapes will be determined in part by the particular intendedapplication and use environment.

DETAILED DESCRIPTION

Reference will now be made in detail to various embodiments of thepresent invention(s), examples of which are illustrated in theaccompanying drawings and described below. While the invention(s) willbe described in conjunction with exemplary embodiments, it will beunderstood that the present description is not intended to limit theinvention(s) to those exemplary embodiments. On the contrary, theinvention(s) is/are intended to cover not only the exemplaryembodiments, but also various alternatives, modifications, equivalentsand other embodiments, which may be included within the spirit and scopeof the invention as defined by the appended claims.

FIG. 1 is a schematic diagram of a planetary gear train according tovarious embodiments of the present invention. Referring to FIG. 1, aplanetary gear train according to various embodiments of the presentinvention includes first, second, third, and fourth planetary gear setsPG1, PG2, PG3, and PG4 arranged on a same axis, an input shaft IS, anoutput shaft OS, nine connecting members TM1 to TM9 for interconnectingrotation elements of the first, second, third, and fourth planetary gearsets PG1, PG2, PG3, and PG4, six control elements C1 to C4 and B1 to B2,and a transmission housing H.

Torque input from the input shaft IS is shifted by cooperative operationof the first, second, third, and fourth planetary gear sets PG1, PG2,PG3, and PG4, and then output through the output shaft OS.

The simple planetary gear sets are arranged in the order of second,third, and fourth planetary gear sets PG1, PG2, PG3, and PG4, from anengine side.

The input shaft IS is an input member and the torque from a crankshaftof an engine, after being torque-converted through a torque converter,is input into the input shaft IS.

The output shaft OS is an output member, and being arranged on a sameaxis with the input shaft IS, delivers a shifted torque to a drive shaftthrough a differential apparatus.

The first planetary gear set PG1 is a single pinion planetary gear set,and includes a first sun gear S1, a first planet carrier PC1 thatsupports a first pinion P1 externally engaged with the first sun gearS1, and a first ring gear R1 internally engaged with the first pinionP1. The first sun gear S1 acts as a first rotation element N1, the firstplanet carrier PC1 acts as a second rotation element N2, and the firstring gear R1 acts as a third rotation element N3.

The second planetary gear set PG2 is a single pinion planetary gear set,and includes a second sun gear S2, a second planet carrier PC2 thatsupports a second pinion P2 externally engaged with the second sun gearS2, and a second ring gear R2 internally engaged with the second pinionP2. The second sun gear S2 acts as a fourth rotation element N4, thesecond planet carrier PC2 acts as a fifth rotation element N5, and thesecond ring gear R2 acts as a sixth rotation element N6.

The third planetary gear set PG3 is a single pinion planetary gear set,and includes a third sun gear S3, a third planet carrier PC3 thatsupports a third pinion P3 externally engaged with the third sun gearS3, and a third ring gear R3 internally engaged with the third pinionP3. The third sun gear S3 acts as a seventh rotation element N7, thethird planet carrier PC3 acts as an eighth rotation element N8, and thethird ring gear R3 acts as a ninth rotation element N9.

The fourth planetary gear set PG4 is a single pinion planetary gear set,and includes a fourth sun gear S4, a fourth planet carrier PC4 thatsupports a fourth pinion P4 externally engaged with the fourth sun gearS4, and a fourth ring gear R4 internally engaged with the fourth pinionP4. The fourth sun gear S4 acts as a tenth rotation element N10, thefourth planet carrier PC4 acts as an eleventh rotation element N11, andthe fourth ring gear R4 acts as a twelfth rotation element N12.

In the first, second, third, and fourth planetary gear sets PG1, PG2,PG3, and PG4, the second rotation element N2 is directly connected withthe eleventh rotation element N11, the fifth rotation element N5 isdirectly connected with the ninth rotation element N9, the sixthrotation element N6 is directly connected with tenth rotation elementN10, by nine connecting members TM1 to TM9.

The nine connecting members TM1 to TM9 are arranged as follows.

The first connecting member TM1 is connected with the first rotationelement N1 (first sun gear S1).

The second connecting member TM2 is connected with the second rotationelement N2 (first planet carrier PC1) and the eleventh rotation elementN11 (fourth planet carrier PC4), and directly connected with the outputshaft OS, thereby continuously acting as an output element.

The third connecting member TM3 is connected with the third rotationelement N3 (first ring gear R1), and directly connected with the inputshaft IS, thereby continuously acting as an input element.

The fourth connecting member TM4 is connected with the fourth rotationelement N4 (second sun gear S2), and directly connected with thetransmission housing H, thereby continuously acting as a fixed element.

The fifth connecting member TM5 is connected with the fifth rotationelement N5 (second planet carrier PC2) and the ninth rotation element N9(third ring gear R3).

The sixth connecting member TM6 is connected with the sixth rotationelement N6 (second ring gear R2) and the tenth rotation element N10(fourth sun gear S4).

The seventh connecting member TM7 is connected with the seventh rotationelement N7 (third sun gear S3), and selectively connected with the thirdconnecting member TM3, thereby acting as a selective input element.

The eighth connecting member TM8 is connected with the eighth rotationelement N8 (third planet carrier PC3), selectively connected with theinput shaft IS and the sixth connecting member TM6, and selectivelyconnected with the transmission housing H.

The ninth connecting member TM9 is connected with the twelfth rotationelement N12 (fourth ring gear R4), selectively connected with the firstconnecting member TM1, and selectively connected with the transmissionhousing H.

The connecting members TM1 to TM9 may be selectively interconnected withone another by control elements of four clutches C1, C2, C3, and C4.

The connecting members TM1 to TM9 may be selectively connected with thetransmission housing H by control elements of two brakes B1 and B2.

The six control elements C1 to C4 and B1 to B2 are arranged as follows.

The first clutch C1 is arranged between the third connecting member TM3and the seventh connecting member TM7, such that the third connectingmember TM3 and the seventh connecting member TM7 may selectively becomeintegral.

The second clutch C2 is arranged between the input shaft IS and theeighth connecting member TM8 is arranged between, such that the inputshaft IS and the eighth connecting member TM8 may selectively becomeintegral.

The third clutch C3 is arranged between the sixth connecting member TM6and the eighth connecting member TM8, such that the sixth connectingmember TM6 and the eighth connecting member TM8 may selectively becomeintegral.

The fourth clutch C4 is arranged between the first connecting member TM1and the ninth connecting member TM9, such that the first connectingmember TM1 and the ninth connecting member TM9 may selectively becomeintegral.

The first brake B1 is arranged between the eighth connecting member TM8and the transmission housing H, such that the eighth connecting memberTM8 may selectively act as a fixed element.

The second brake B2 is arranged between the ninth connecting member TM9and the transmission housing H, such that the ninth connecting memberTM9 may selectively act as a fixed element.

The control elements of the first, second, third, and fourth clutchesC1, C2, C3, and C4 and the first and second brakes B1 and B2 may berealized as multi-plate hydraulic pressure friction devices that arefrictionally engaged by hydraulic pressure.

FIG. 2 is an operational chart for respective control elements atrespective shift stages in a planetary gear train according to variousembodiments of the present invention. As shown in FIG. 2, a planetarygear train according to various embodiments of the present inventionperforms shifting by operating three control elements at respectiveshift stages.

In the forward first speed D1, the first and third clutches C1 and C3and the second brake B2 are simultaneously operated. As a result, thethird connecting member TM3 is interconnected with the seventhconnecting member TM7 by the operation of the first clutch C1, and thesixth connecting member TM6 is interconnected with the eighth connectingmember TM8 by the operation of the third clutch C3. In this state,torque is input to the third connecting member TM3. In addition, whilethe fourth connecting member TM4 is acting as a fixed element, the ninthconnecting member TM9 simultaneously acts as a fixed element by theoperation of the second brake B2, thereby realizing the forward firstspeed and outputting a shifted torque through the output shaft OSconnected with the second connecting member TM2.

In the forward second speed D2, the second and third clutches C2 and C3and the second brake B2 are simultaneously operated. As a result, theinput shaft IS is interconnected with the eighth connecting member TM8by the operation of the second clutch C2, and the sixth connectingmember TM6 is interconnected with the eighth connecting member TM8 bythe operation of the third clutch C3. In this state, torque is input tothe third and eighth connecting member TM3 and TM8. In addition, whilethe fourth connecting member TM4 is acting as a fixed element, the ninthconnecting member TM9 simultaneously acts as a fixed element by theoperation of the second brake B2, thereby realizing the forward secondspeed and outputting a shifted torque through the output shaft OSconnected with the second connecting member TM2.

In the forward third speed D3, the first and second clutches C1 and C2and the second brake B2 are simultaneously operated. As a result, thethird connecting member TM3 is interconnected with the seventhconnecting member TM7 by the operation of the first clutch C1, and theinput shaft IS is interconnected with the eighth connecting member TM8by the operation of the second clutch C2. In this state, torque is inputto the third and eighth connecting members TM3 and TM8. In addition,while the fourth connecting member TM4 is acting as a fixed element, theninth connecting member TM9 simultaneously acts as a fixed element bythe operation of the second brake B2, thereby realizing the forwardthird speed and outputting a shifted torque through the output shaft OSconnected with the second connecting member TM2.

In the forward fourth speed D4, the first and fourth clutches C1 and C4and the second brake B2 are simultaneously operated. As a result, thethird connecting member TM3 is interconnected with the seventhconnecting member TM7 by the operation of the first clutch C1, and thefirst connecting member TM1 is interconnected with the ninth connectingmember TM9 by the operation of the fourth clutch C4. In this state,torque is input to the third connecting member TM3. In addition, whilethe fourth connecting member TM4 is acting as a fixed element, thefirst, ninth connecting member TM1 and TM9 simultaneously acts as afixed element by the operation of the second brake B2, thereby realizingthe forward fourth speed and outputting a shifted torque through theoutput shaft OS connected with the second connecting member TM2.

In the forward fifth speed D5, the first, second, and fourth clutchesC1, C2, and C4 are simultaneously operated. As a result, the thirdconnecting member TM3 is interconnected with the seventh connectingmember TM7 by the operation of the first clutch C1, the input shaft ISis interconnected with the eighth connecting member TM8 by the operationof the second clutch C2, and the first connecting member TM1 isinterconnected with the ninth connecting member TM9 by the operation ofthe fourth clutch C4. In this state, torque is input to the third andeighth connecting members TM3 and TM8. In addition, the fourthconnecting member TM4 acts as a fixed element, thereby realizing theforward fifth speed and outputting a shifted torque through the outputshaft OS connected with the second connecting member TM2.

In the forward sixth speed D6, the second, third, and fourth clutchesC2, C3, and C4 are simultaneously operated. As a result, the input shaftIS is interconnected with the eighth connecting member TM8 by theoperation of the second clutch C2, the sixth connecting member TM6 isinterconnected with the eighth connecting member TM8 by the operation ofthe third clutch C3, the first connecting member TM1 is interconnectedwith the ninth connecting member TM9 by the operation of the fourthclutch C4. Therefore, the first, second, third, and fourth planetarygear sets PG1, PG2, PG3, and PG4 becomes integral as a whole, therebyrealizing the forward sixth speed and outputting a shifted torqueexactly as input, through the output shaft OS connected with the secondconnecting member TM2.

In the forward seventh speed D7, the first, third, and fourth clutchesC1, C3, and C4 are simultaneously operated. As a result, the thirdconnecting member TM3 is interconnected with the seventh connectingmember TM7 by the operation of the first clutch C1, the sixth connectingmember TM6 is interconnected with the eighth connecting member TM8 bythe operation of the third clutch C3, and the first connecting memberTM1 is interconnected with the ninth connecting member TM9 by theoperation of the fourth clutch C4. In this state, torque is input to thethird connecting member TM3. In addition, the fourth connecting memberTM4 acts as a fixed element, thereby realizing the forward seventh speedand outputting a shifted torque through the output shaft OS connectedwith the second connecting member TM2.

In the forward eighth speed D8, the third and fourth clutches C3 and C4and the first brake B1 are simultaneously operated. As a result, thesixth connecting member TM6 is interconnected with the eighth connectingmember TM8 by the operation of the third clutch C3, and the firstconnecting member TM1 is interconnected with the ninth connecting memberTM9 by the operation of the fourth clutch C4. In this state, torque isinput to the third connecting member TM3. In addition, while the fourthconnecting member TM4 is acting as a fixed element, the eighthconnecting member TM8 simultaneously acts as a fixed element by theoperation of the first brake B1, thereby realizing the forward eighthspeed and outputting a shifted torque through the output shaft OSconnected with the second connecting member TM2.

In the forward ninth speed D9, the first and fourth clutches C1 and C4and the first brake B1 are simultaneously operated. As a result, thethird connecting member TM3 is interconnected with the seventhconnecting member TM7 by the operation of the first clutch C1, and thefirst connecting member TM1 is interconnected with the ninth connectingmember TM9 by the operation of the fourth clutch C4. In this state,torque is input to the third connecting member TM3. In addition, whilethe fourth connecting member TM4 is acting as a fixed element, theeighth connecting member TM8 simultaneously acts as a fixed element bythe operation of the first brake B1, thereby realizing the forward ninthspeed and outputting a shifted torque through the output shaft OSconnected with the second connecting member TM2.

In the reverse speed REV, the first clutch C1 and the first and secondbrakes B1 and B2 are simultaneously operated. As a result, the thirdconnecting member TM3 is interconnected with seventh connecting memberTM7 by the operation of the first clutch C1, and torque is input to thethird connecting member TM3. In addition, while the fourth connectingmember TM4 is acting as a fixed element, the eighth connecting memberTM8 and the ninth connecting member TM9 also act as fixed elements bythe operation of the first and second brakes B1 and B2, therebyrealizing the reverse speed and outputting a shifted torque through theoutput shaft OS connected with the second connecting member TM2.

As described above, a planetary gear train according to variousembodiments of the present invention realizes at least nine forwardspeeds and at least one reverse speed formed by operating the fourplanetary gear sets PG1, PG2, PG3, and PG4 by controlling the fourclutches C1, C2, C3, and C4 and the two brakes B1 and B2.

In addition, a planetary gear train according to various embodiments ofthe present invention realizes a gear ratio span of more than 8.0,thereby maximizing efficiency of driving an engine.

In addition, the linearity of step ratios of shift stages is securedwhile multi-staging the shift stage with high efficiency, thereby makingit possible to improve drivability such as acceleration before and aftera shift, an engine speed rhythmic sense, and the like.

The foregoing descriptions of specific exemplary embodiments of thepresent invention have been presented for purposes of illustration anddescription. They are not intended to be exhaustive or to limit theinvention to the precise forms disclosed, and obviously manymodifications and variations are possible in light of the aboveteachings. The exemplary embodiments were chosen and described in orderto explain certain principles of the invention and their practicalapplication, to thereby enable others skilled in the art to make andutilize various exemplary embodiments of the present invention, as wellas various alternatives and modifications thereof. It is intended thatthe scope of the invention be defined by the Claims appended hereto andtheir equivalents.

What is claimed is:
 1. A planetary gear train of an automatictransmission for a vehicle, comprising: an input shaft configured forreceiving an engine torque; an output shaft configured for outputting ashifted torque; a first planetary gear set including first, second, andthird rotation elements; a second planetary gear set including fourth,fifth, and sixth rotation elements; a third planetary gear set includingseventh, eighth, and ninth rotation elements; a fourth planetary gearset including tenth, eleventh, and twelfth rotation elements; and sixcontrol elements for selectively interconnecting the rotation elementsand a transmission housing, wherein the input shaft is continuouslyconnected to the third rotation element and selectively connected toeighth rotation element, the output shaft is continuously connected tothe second rotation element and the eleventh rotation element, thefourth rotation element is continuously connected to the transmissionhousing, the fifth rotation element is continuously connected to theninth rotation element, the sixth rotation element is continuouslyconnected to the tenth rotation element, and at least nine forwardspeeds and at least one reverse speed are achieved by controlling threeof the six control elements.
 2. The planetary gear train of claim 1,wherein the third rotation element is selectively connected to theseventh rotation element by a first clutch; the eighth rotation elementis selectively connected to the input shaft by a second clutch; thesixth rotation element is selectively connected to the eighth rotationelement by a third clutch; the first rotation element is selectivelyconnected to the twelfth rotation element by a fourth clutch; the eighthrotation element is selectively connected to the transmission housing bya first brake; and the twelfth rotation element is selectively connectedto the transmission housing by a second brake.
 3. The planetary geartrain of claim 1, wherein the first, second, and third rotation elementsare respectively a sun gear, a planet carrier, and a ring gear of thefirst planetary gear set; the fourth, fifth, and sixth rotation elementsare respectively a sun gear, a planet carrier, and a ring gear of thesecond planetary gear set; the seventh, eighth, and ninth rotationelements are respectively a sun gear, a planet carrier, and a ring gearof the third planetary gear set; and the tenth, eleventh, and twelfthrotation elements are respectively a sun gear, a planet carrier, and aring gear of the fourth planetary gear set.
 4. A planetary gear train ofan automatic transmission for a vehicle, comprising: an input shaftconfigured for receiving an engine torque; an output shaft configuredfor outputting a shifted torque; a first planetary gear set includingfirst, second, and third rotation elements; a second planetary gear setincluding fourth, fifth, and sixth rotation elements; a third planetarygear set including seventh, eighth, and ninth rotation elements; afourth planetary gear set including tenth, eleventh, and twelfthrotation elements; six control elements for selectively interconnectingthe rotation elements and a transmission housing; a first connectingmember connected to the first rotation element; a second connectingmember connected to the second rotation element and the eleventhrotation element and directly connected to the output shaft; a thirdconnecting member connected to the third rotation element and directlyconnected to the input shaft; a fourth connecting member connected tothe fourth rotation element and directly connected to the transmissionhousing; a fifth connecting member connected to the fifth rotationelement and the ninth rotation element; a sixth connecting memberconnected to the sixth rotation element and the tenth rotation element;a seventh connecting member connected to the seventh rotation elementand selectively connected to the third connecting member; an eighthconnecting member connected to the eighth rotation element, selectivelyconnected to the input shaft and the sixth connecting member, andselectively connected to the transmission housing; and a ninthconnecting member connected to the twelfth rotation element, selectivelyconnected to the first connecting member, and selectively connected totransmission housing.
 5. The planetary gear train of claim 4, whereinthe first planetary gear set is a single pinion planetary gear set,where the first rotation element is a first sun gear, the secondrotation element is a first planet carrier, and the third rotationelement is a first ring gear; the second planetary gear set is a singlepinion planetary gear set, where the fourth rotation element is a secondsun gear, the fifth rotation element is a second planet carrier, and thesixth rotation element is a second ring gear; the third planetary gearset is a single pinion planetary gear set, where the seventh rotationelement is a third sun gear, the eighth rotation element is a thirdplanet carrier, and the ninth rotation element is a third ring gear; andthe fourth planetary gear set is a single pinion planetary gear set,where the tenth rotation element is a fourth sun gear, the eleventhrotation element is a fourth planet carrier, and the twelfth rotationelement is a fourth ring gear.
 6. The planetary gear train of claim 4,wherein the six control elements comprise: a first clutch selectivelyconnecting the third connecting member and the seventh connectingmember; a second clutch selectively connecting the input shaft and theeighth connecting member; a third clutch selectively connecting thesixth connecting member and the eighth connecting member; a fourthclutch selectively connecting the first connecting member and the ninthconnecting member; a first brake selectively connecting the eighthconnecting member and the transmission housing; and a second brakeselectively connecting the ninth connecting member and the transmissionhousing.
 7. The planetary gear train of claim 6, wherein shift stagesrealized by selective operation of the six control elements comprise: aforward first speed formed by operation of the first and third clutchesand the second brake; a forward second speed formed by operation of thesecond and third clutches and the second brake; a forward third speedformed by operation of the first clutch and second clutch and the secondbrake; a forward fourth speed formed by operation of the first andfourth clutches and the second brake; a forward fifth speed formed byoperation of the first, second, and fourth clutches; a forward sixthspeed formed by operation of the second, third, and fourth clutches; aforward seventh speed formed by operation of the first, third, andfourth clutches; a forward eighth speed formed by operation of the thirdand fourth clutches and the first brake; a forward ninth speed formed byoperation of the first and fourth clutches and the first brake; and areverse speed formed by operation of the first clutch and the first andsecond brakes.
 8. A planetary gear train of an automatic transmissionfor a vehicle, comprising: an input shaft configured for receiving anengine torque; an output shaft configured for outputting a shiftedtorque; a first planetary gear set as a single pinion planetary gear setincluding first, second, and third rotation elements; a second planetarygear set as a single pinion planetary gear set including fourth, fifth,and sixth rotation elements; a third planetary gear set as a singlepinion planetary gear set including seventh, eighth, and ninth rotationelements; a fourth planetary gear set as a single pinion planetary gearset including tenth, eleventh, and twelfth rotation elements; a firstconnecting member connected to the first rotation element; a secondconnecting member connected to the second rotation element and theeleventh rotation element and directly connected to the output shaft; athird connecting member connected to the third rotation element anddirectly connected to the input shaft; a fourth connecting memberconnected to the fourth rotation element and directly connected to thetransmission housing; a fifth connecting member connected to the fifthrotation element and the ninth rotation element; a sixth connectingmember connected to the sixth rotation element and the tenth rotationelement; a seventh connecting member connected to the seventh rotationelement and selectively connected to the third connecting member; aneighth connecting member connected to the eighth rotation element,selectively connected to the input shaft and the sixth connectingmember, and selectively connected to the transmission housing; a ninthconnecting member connected to the twelfth rotation element, selectivelyconnected to the first connecting member, and selectively connected totransmission housing; a first clutch selectively connecting the thirdconnecting member and the seventh connecting member; a second clutchselectively connecting the input shaft and the eighth connecting member;a third clutch selectively connecting the sixth connecting member andthe eighth connecting member; a fourth clutch selectively connecting thefirst connecting member and the ninth connecting member; a first brakeselectively connecting the eighth connecting member and the transmissionhousing; and a second brake selectively connecting the ninth connectingmember and the transmission housing.
 9. The planetary gear train ofclaim 8, wherein the first planetary gear set includes a first sun gearas the first rotation element, a first planet carrier as the secondrotation element, and a first ring gear as the third rotation element;the second planetary gear set includes a second sun gear as the fourthrotation element, a second planet carrier as the fifth rotation element,and a second ring gear as the sixth rotation element; the thirdplanetary gear set includes a third sun gear as the seventh rotationelement, a third planet carrier as the eighth rotation element, and athird ring gear as the ninth rotation element; and the fourth planetarygear set includes a fourth sun gear as the tenth rotation element, afourth planet carrier as the eleventh rotation element, and a fourthring gear as the twelfth rotation element.
 10. The planetary gear trainof claim 8, wherein shift stages realized by selective operation of thefour clutches and the two brakes comprise: a forward first speed formedby operation of the first and third clutches and the second brake; aforward second speed formed by operation of the second and thirdclutches and the second brake; a forward third speed formed by operationof the first clutch and second clutch and the second brake; a forwardfourth speed formed by operation of the first and fourth clutches andthe second brake; a forward fifth speed formed by operation of thefirst, second, and fourth clutches; a forward sixth speed formed byoperation of the second, third, and fourth clutches; a forward seventhspeed formed by operation of the first, third, and fourth clutches; aforward eighth speed formed by operation of the third and fourthclutches and the first brake; a forward ninth speed formed by operationof the first and fourth clutches and the first brake; and a reversespeed formed by operation of the first clutch and the first and secondbrakes.
 11. A planetary gear train of an automatic transmission for avehicle, comprising: an input shaft configured for receiving an enginetorque; an output shaft configured for outputting a shifted torque; afirst planetary gear set as a single pinion planetary gear set includinga first sun gear, a first planet carrier, and a first ring gear; asecond planetary gear set as a single pinion planetary gear setincluding a second sun gear, a second planet carrier, and a second ringgear; a third planetary gear set as a single pinion planetary gear setincluding a third sun gear, a third planet carrier, and a third ringgear; a fourth planetary gear set as a single pinion planetary gear setincluding a fourth sun gear, a fourth planet carrier, and a fourth ringgear; a first connecting member connected to the first sun gear; asecond connecting member connected to the first planet carrier and thefourth planet carrier and directly connected to the output shaft; athird connecting member connected to the first ring gear and directlyconnected to the input shaft; a fourth connecting member connected tothe second sun gear and directly connected to the transmission housing;a fifth connecting member connected to the second planet carrier and thethird ring gear; a sixth connecting member connected to the second ringgear and the fourth sun gear; a seventh connecting member connected tothe third sun gear and selectively connected to the third connectingmember; an eighth connecting member connected to the third planetcarrier, selectively connected to the input shaft and the sixthconnecting member, and selectively connected to transmission housing; aninth connecting member connected to the fourth ring gear, selectivelyconnected to the first connecting member, and selectively connected tothe transmission housing; and six control elements selectivelyconnecting the connecting members and the transmission housing.
 12. Theplanetary gear train of claim 11, wherein the six control elementscomprise: a first clutch selectively connecting the third connectingmember and the seventh connecting member; a second clutch selectivelyconnecting the input shaft and the eighth connecting member; a thirdclutch selectively connecting the sixth connecting member and the eighthconnecting member; a fourth clutch selectively connecting the firstconnecting member and the ninth connecting member; a first brakeselectively connecting the eighth connecting member and the transmissionhousing; and a second brake selectively connecting the ninth connectingmember and the transmission housing.
 13. The planetary gear train ofclaim 12, wherein shift stages realized by selective operation of thesix control elements comprise: a forward first speed formed by operationof the first and third clutches and the second brake; a forward secondspeed formed by operation of the second and third clutches and thesecond brake; a forward third speed formed by operation of the firstclutch and second clutch and the second brake; a forward fourth speedformed by operation of the first and fourth clutches and the secondbrake; a forward fifth speed formed by operation of the first, second,and fourth clutches; a forward sixth speed formed by operation of thesecond, third, and fourth clutches; a forward seventh speed formed byoperation of the first, third, and fourth clutches; a forward eighthspeed formed by operation of the third and fourth clutches and the firstbrake; a forward ninth speed formed by operation of the first and fourthclutches and the first brake; and a reverse speed formed by operation ofthe first clutch and the first and second brakes.